1. Field of the Invention
This invention relates to a continuous mining machine and more particularly to a mining machine having a cutter drum assembly that includes an intermediate drum section positioned between a pair of end drum sections in which the intermediate drum section is nonrotatably connected to drive shafts in a manner to facilitate efficient assembly and disassembly thereon.
2. Description of the Prior Art
Continuous mining machines, as illustrated in U.S. Pat. No. 3,774,969, are utilized in underground mining operations to continuously dislodge solid mineral material from the face of a mine shaft. Generally, a boom member extends forwardly from an elongated body portion of the mining machine that is propelled through the mine on endless crawler tracks. The boom member is pivotally connected to the mining machine body portion and rotatably supports a cutter drum assembly having peripherally extending cutting elements. The cutter drum assembly extends transversely to the longitudinal axis of the body portion and upon rotation, the cutting elements dislodge solid material from the mine face.
The cutter drum assembly is raised to a preselected vertical height in the mine as determined by the thickness of the mineral seam. The cutter drum assembly is rotated and sumped into the mine face with the cutter drum assembly positioned adjacent the mine roof. Once the cutter drum assembly has advanced into the mine face, the boom member is pivoted downwardly to move the cutter drum assembly vertically downwardly through the face to make a shear cut in the face. The dislodged material is gathered by a gathering device which moves the dislodged material rearwardly onto a conveyor that extends longitudinally on the mining machine to transport the material toward the rear of the mining machine. By dislodging mineral material from the mine face in this manner a mine passageway or room is formed to thus permit the mining machine to advance and continuously dislodge material from the mine face.
It is the conventional practice to position the cutting elements on the periphery of the cutter drum assembly in a continuous screw-type pattern. The material dislodged by the cutting elements is also conveyed by the cutting elements inwardly from the end drum sections to the center of the intermediate drum section and fed onto the gathering device. Each of the cutting elements includes a cutter bit positioned in a bit holder which is supported by a bit block.
The bit block may be mounted on the periphery of the cutter drum in a number of ways, such as by welding the bit block to the surface of the cutter drum. In this manner the cutting elements are permanently affixed to the cutter drum. However, the cutter bits are subject to wear and breakage, thereby requiring frequent replacement which may be required on a daily basis. Therefore, to facilitate the replacement of broken cutter bits removable retaining means, as disclosed in U.S. Pat. No. Re. 28,310, have been developed for securing the cutter bits in the bit holder so that the bits can be quickly installed or removed and replaced.
Not only are the cutter bits subject to failure but the bit holder and the bit block as well. Because the bit holder and block of each cutting element are subject to the stresses of the cutting action, it is not unusual to require their replacement on a weekly basis. Since the bit block is usually welded to the cutter drum assembly its replacement is difficult. It is the conventional practice when possible to replace a bit block by welding in the field. Frequently, however, it is necessary to remove the mining machine from service in the mine and take it to a place where repairs can be made. Both of these methods of replacing a bit block are time consuming and result in considerable downtime for the mining machine. Consequently, repair of broken bit blocks or bit holders is postponed until the efficiency of the mining machine is diminished to the point where the mining machine can no longer function properly without making the necessary repair.
One alternative to removing the mining machine from its place of operation in the mine in order to replace broken bit blocks is disassembly of the required portion of the cutter drum housing and installation of a replacement housing at the location of operation of the mining machine. This avoids the delays encountered when the machine is moved from the mine face to a repair point remote from the face. However, with the known continuous mining machines as above described and also disclosed in U.S. Pat. Nos. 2,758,826; 3,290,096 and 3,773,384 the intermediate and end drum sections are formed by a cylindrical casing or shell providing a hollow cavity into which the drum drive shafts extend. Removing the cylindrical shell is difficult, particularly when the mining machine is positioned at the mine face where there is limited space available to disassemble the cutter drum. Also, with known cutter drums when disassembled the bearing seals are exposed and the lubricant is lost.
One solution suggested to this problem is disclosed in U.S. Pat. No. 3,307,880 in which the cutter bits are carried in a bit holder which is in the form of split ring sections. The split ring sections are bolted together and clamped onto the periphery of the cutter drum. This arrangement permits the removal and replacement of the split ring sections without removing other parts of the cutter drum for sharpening dull bits and replacing damaged bit holders. However, the housing of the cutter drum is not adapted for efficient dismantling.
There is need for a continuous mining machine having a cutter drum assembly which is readily assembled and disassembled for repair of broken cutting elements on the periphery of the cutter drum so the continuous mining machine may remain at its place of operation in the mine and thus reduce the downtime for repairing the broken cutting elements. While it has been suggested to provide a replacable cutting elements on the periphery of the cutter drum, the prior art devices do not provide a cutter drum assembly that is capable of being efficiently disassembled at its location of operation without considerable difficulty and without exposing the bearing seals to possible damage.